Calculate your baby's estimated delivery date (EDD), current gestational age in weeks and days, trimester timeline, and developmental milestones based on LMP, ultrasound, conception date, or IVF transfer.
Adjusts Naegele's rule based on your cycle length (+280 days + cycle length - 28 days).
Only ~4% of babies are born on their exact calculated due date. Deliveries between 37 and 42 weeks are clinically considered healthy full-term births.
Rapid organogenesis, neural tube closure, and primitive heartbeat development.
Rapid fetal skeletal growth, quickening movements, and mid-pregnancy anatomy survey.
Lung surfactant maturation, rapid brain expansion, and substantial weight gain.
Calculated calendar dates from baseline LMP through delivery:
Obstetric dating baseline marker from which the 280-day gestational clock begins.
Fertilization of mature ovum by spermatozoon in the fallopian tube, creating a zygote.
Rhythmic cardiac contractions visible via transvaginal ultrasound (100–160 bpm).
Critical organogenesis complete; placenta fully operational; baseline miscarriage risk drops significantly.
Comprehensive level II structural ultrasound examining fetal heart, brain, spine, kidneys, and fetal sex.
Lungs begin producing surfactant; modern neonatal intensive care (NICU) viability threshold reached.
Fetus opens eyelids, establishes regular sleep-wake cycles, and practices rhythmic breathing reflexes.
Baby is considered fully developed; unassisted extrauterine breathing and feeding are safe.
Official 40-week delivery milestone (280 days from LMP / 266 days post-conception).
Post-due milestone where antenatal biophysical profiles and amniotic fluid monitoring are conducted.
Medically reviewed clinical principles of gestational dating according to the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM).
An Estimated Due Date (EDD) is a statistical benchmark representing the completion of 280 days (40 full weeks) from the first day of your last menstrual period. It does not represent an expiration date or a guaranteed delivery appointment:
Large-scale clinical registry studies consistently demonstrate that only approximately 4% of women spontaneously deliver on their exact calculated due date. Around 80% of babies arrive within a 2-week window (from 38 to 42 weeks).
Calendar months average 30.4 days. 40 weeks equals 280 days, which is approximately 9 calendar months plus 1 week. Because clinical dating starts at the beginning of the menstrual cycle before conception, the baby spends 38 weeks (266 days) developing inside the uterus.
Answers to common obstetric questions regarding due dates, cycle variation, and delivery timing.
This Due Date Calculator is intended strictly for educational and informational purposes based on standard obstetric formulas endorsed by the American College of Obstetricians and Gynecologists (ACOG). Estimated dates are statistical averages and do not represent a diagnosis or guaranteed delivery time. Always consult with a licensed obstetrician-gynecologist (OB-GYN), certified nurse-midwife, or healthcare professional for individualized prenatal care and clinical biometric ultrasound evaluation.